The invention relates to curable compositions resulting from the hydrosilation of olefin-containing polymers with organosiloxane hydrides. The curable compositions may be cured to provide low surface energy cured compositions which may be provided in the form of a coating on a substrate.
Coatings having low surface energy are well known for use as automotive waxes, marine waxes and antifouling coatings. These coatings are useful because the low surface energy inhibits attachment of marine organisms and causes water to bead and to run off the surface of the coating. Silicone containing materials are known to provide low surface energy when incorporated into coatings. However, when low molecular weight silicone containing additives are used as the means of incorporating silicone into a coating, leaching of the silicone containing additive may result. Over time, this leaching leads to an increase in the surface energy of the coating and, consequently, a reduction in the performance of the coating. Silicone based polymers themselves are of little use since they typically lack the mar and abrasion resistance needed for these applications.
Theoretically, an ideal material for durable low surface energy coatings would have a strong polymer backbone with multiple silicone containing substituents grafted onto the polymer backbone at various points along its length. Gabor et al. report the hydrosilation of styrene-butadiene block co-polymers with organosiloxane monohydrides such as pentamethyldisiloxane or 1,1,1,3,3,5,5-heptamethyl trisiloxane. The resulting polymers have linear silicon-containing pendant chains (see, Gabor et al., Polym. Prepr. (ACS Div. Poly. Chem.), 1992, 33 (2), pp. 136-137). The short chain organosiloxanes monohydrides provide only a low level of silicone in the resulting polymers.
U.S. Pat. No. 5,703,163 (Baum) reports loop polymers having a polymeric backbone and a plurality of olefinic groups which have been converted to closed loops by reaction with difunctional organic compounds reactive with the olefinic groups. Although Baum incorporates a higher level of silicone into the resulting polymers, the synthetic scheme used to form loop polymers is preferably carried out at low percent solids. This limitation complicates commercial use of the resulting loop polymers as they must be recovered from a large amount of solvent in order to be useful in high solids coating formulations.
In view of the foregoing, there is a need for curable compositions having a high level of silicone chemically grafted onto a polymer backbone that can be manufactured at high solids without the formation of an solid mass and/or insoluble gel. A synthetic route that eliminates gel formation resulting from excessive crosslinking and yields a high percent solids curable composition is highly desirablc.